Normal embryology of the respiratory system Sept28 M3

Question 1

embryonic origin of resp lining epithelium (trachea, bronchi, alveoli)

Answer 1

embryonic endoderm

Question 2

embryo origin of pleural cavity

Answer 2

embryonic mesoderm

Question 3

when pleural cavity formed

Answer 3

very early in embryogenesis (flat trilaminar embryo phase) in the intra embryonic mesenchyme

Question 4

how trilaminar embryo fols 3 body cavities

Answer 4

forms horseshoe-shaped cavity that divides into pericardial cavity, pleural (thorax) and peritoneal (abdominal-pelvic region)

Question 5

cavities formed after the horseshoe-shaped cavity separates

Answer 5

pericardial, left and right pleural cavity, left and right peritoneal cavity

Question 6

because the cavities are formed from mesenchyme, we’ll say that a ___________ is formed

Answer 6

mesothelium

Question 7

what lines cavities and why

Answer 7

coelomic epithelium because the cavity forms in the mesenchyme

Question 8

4 week embryo: result

Answer 8

cylindrical embryo envelopped in fluid filled amniotic sac

primitive organ systems are enveloped in the 3 definitive body cavities by intra-embryonic coelom

Question 9

how primitive gut forms

Answer 9

• have amniotic cavity that expands in extra-embryonic cavity
• yolk sac protrudes in space between yolk sac and amniotic cavity to form foregut, midgut, hindgut

Question 10

embryonic origin of the primitive gut and why

Answer 10

endoderm (bc are expansion of yolk sac)

Question 11

origin of the respiratory system and important thing to form it

Answer 11

foregut. Amniotic fluid plays an important role

Question 12

organs that the foregut produces

Answer 12

pharynx, esophagus, resp system, stomach, proximal duodenum, liver, pancreas

Question 13

why diaphragm formation is important

Answer 13

provides comparmentalization, to make space for lungs and separate thorax from abdomen

Question 14

what provides gaseous exchange prenatally

Answer 14

placenta

Question 15

structures of the primitive gut

Answer 15

buccopharyngeal membrane, foregut, midgut, hindgut, cloacal membrane

Question 16

how the gut is canalized

Answer 16

apoptosis from buccopharyngeal membrane (week 4) to cloacal membrane (week 7)

Question 17

where undetached pleural cavity is present near the primitive gut

Answer 17

on sides of the foregut

Question 18

what is the septum transversum

Answer 18

mesenchyme on which the heart and pericardial cavity lies and that is continuous with the forming membrane that will separate the pleura and peritoneal cavity

Question 19

what diaphragm comes from and why

Answer 19

from septum transversum, it is the membrane that separates pleural and peritoneal cavity.

Question 20

origin of septum transversum

Answer 20

mesenchyme that came from cervical region and migrated to reach its position. Took with it nerves from cervical spinal cord

Question 21

consequence of herniation through the diaphragm

Answer 21

hypoplasia of the lungs bc abdominal organs herniate into thoracic cavity

Question 22

common sites of herniation through diaphragm

Answer 22

• through pleuro-peritoneal membrane on left of the mediastinum (Foramen of Bochdalek)
• anteriorly and parasternally (Formane of Morgagni x2)

Question 23

important factor determining if embryonic herniation will be viable

Answer 23

time of closure of foramens of Bochdalek and Morgagni.

• Early herniation: severe hypoplasia-death.
• Midler defect-weakness could simply appear later in life

Question 24

Respiratory system origin

Answer 24

endoderm and foregut

Question 25

After cavities seaprate and diaphragm present, how lungs develop and what diaphragm does

Answer 25

will start branching. diaphragm starts to contract

Question 26

initial structure where trachea and bronchi will come from

Answer 26

foregut, primitive pharynx: splanchnopleure (mesenchyme) surrounds foregut in which endodermal apoptosis is occuring

Question 27

first step to trachea and bronchi formation

Answer 27

laryngo-tracheal groove forms and its bottom is a tracheo-esophageal septum

Question 28

2nd step to trachea and bronchi formation

Answer 28

laryngo-tracheal groove creates lung buds (branches) at the bottom

Question 29

what allows pinching off of the trachea

Answer 29

trachea-esophageal mesenchyme. interacts with the endoderm and it’s genetically controlled